A dielectric barrier discharge type low-pressure discharge lamp having an electrode on the outer surface of a tubular glass lamp vessel (EEFL) is known as an example which is described in the laid-open Japanese utility model application Shou 61-126559, for example. This low-pressure discharge lamp is charged with ionizable filler such as rare gas or mixed gas of mercury and rare gas inside a tubular glass lamp vessel with both ends sealed. On the inner wall surface of the tubular glass lamp vessel, a phosphor layer is formed as necessary. On the outer surfaces of both ends of the tubular glass lamp vessel, external electrodes are arranged.
The external electrodes are composed of, for example, a metallic tape made of aluminum foil and a conductive adhesive for forming an electrically conductive layer and coiled lead wires connected to the metallic tape, which acts as a metal fitting for supplying the low-pressure discharge lamp with an electric power. Here, the coiled lead wires are made contact with the metallic tapes by their own elasticity.
The low-pressure discharge lamp having such a structure has an advantage that no electrode is provided in the tubular glass lamp vessel, so that no electrode consumption is caused and the life is long. However, since the diameter of the tubular glass lamp vessel is very small such as about 3 mm, a complicated machine is required to apply the metallic tape on the tubular glass lamp vessel with high dimensional accuracy and it is difficult to manufacture the discharge lamps in mass production.
Further, in an electrode using such a metallic tape, a power loss is caused in the conductive adhesive made of acrylic resin when a current flows through the metallic tape, and there is a defect of increasing in the power consumption of the lamp.
Furthermore, since the conductive adhesive has low heat resistance, it is partially carbonized due to generation of heat when the current flows, and the resistance of the part is reduced, where the current is concentrated. As a result, a problem arises that intense heat is generated, and the tubular glass lamp vessel is partially fused to form a hole.
According to embodiments of the present invention, the low-pressure discharge lamp having an electrode using a conventional metallic tape is provided, with which such technical problems as high power consumption or forming the hole of are solved and which is capable of adopting a manufacturing method for realizing mass production at low cost.